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Localized carbon deposition in solid oxide electrolysis cells studied by multiphysics modeling

Navasa, Maria LU ; Frandsen, Henrik Lund; Skafte, Theis Løye; Sundén, Bengt LU and Graves, Christopher (2018) In Journal of Power Sources 394. p.102-113
Abstract

Solid oxide electrochemical cells (SOCs) can store electrical energy in the form of chemical fuels with high efficiency by electrolysis of CO2 and H2O. However, achieving commercially relevant lifetime is hindered by degradation mechanisms such as carbon deposition, which can even destroy the cell especially during electrolysis where carbon formation is electrochemically driven at the electrode-electrolyte interface. Here we used a three-dimensional multiphysics model to simulate a SOC performing CO2 electrolysis and determine the operating conditions and locations in the porous nickel-based electrodes where carbon deposition is expected based on local conditions (gas composition, temperature and... (More)

Solid oxide electrochemical cells (SOCs) can store electrical energy in the form of chemical fuels with high efficiency by electrolysis of CO2 and H2O. However, achieving commercially relevant lifetime is hindered by degradation mechanisms such as carbon deposition, which can even destroy the cell especially during electrolysis where carbon formation is electrochemically driven at the electrode-electrolyte interface. Here we used a three-dimensional multiphysics model to simulate a SOC performing CO2 electrolysis and determine the operating conditions and locations in the porous nickel-based electrodes where carbon deposition is expected based on local conditions (gas composition, temperature and overpotential) crossing local thermodynamic thresholds. It is found that CO/CO2 gas diffusion gradients and cooling from the endothermic electrolysis reaction are important driving forces for carbon deposition to occur locally when it is not expected based on the outlet CO concentration. Furthermore, correlation with a set of experimentally determined threshold operating points indicates that carbon deposition occurs primarily by the Boudouard reaction rather than by direct electrochemical reduction of CO or CO2 to carbon for the studied cell type. Variation of fuel electrode porosity and thickness shows that these methods of reducing gas diffusion limitations widen the operating window that avoids carbon deposition.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Boudouard reaction, Carbon deposition, Multiphysics modeling, SOEC, Thermodynamic threshold
in
Journal of Power Sources
volume
394
pages
12 pages
publisher
Elsevier
external identifiers
  • scopus:85047269840
ISSN
0378-7753
DOI
10.1016/j.jpowsour.2018.05.039
language
English
LU publication?
yes
id
5b868a5f-5cc4-48a7-af82-c322a056e954
date added to LUP
2018-05-31 14:08:23
date last changed
2019-07-16 03:50:59
@article{5b868a5f-5cc4-48a7-af82-c322a056e954,
  abstract     = {<p>Solid oxide electrochemical cells (SOCs) can store electrical energy in the form of chemical fuels with high efficiency by electrolysis of CO<sub>2</sub> and H<sub>2</sub>O. However, achieving commercially relevant lifetime is hindered by degradation mechanisms such as carbon deposition, which can even destroy the cell especially during electrolysis where carbon formation is electrochemically driven at the electrode-electrolyte interface. Here we used a three-dimensional multiphysics model to simulate a SOC performing CO<sub>2</sub> electrolysis and determine the operating conditions and locations in the porous nickel-based electrodes where carbon deposition is expected based on local conditions (gas composition, temperature and overpotential) crossing local thermodynamic thresholds. It is found that CO/CO<sub>2</sub> gas diffusion gradients and cooling from the endothermic electrolysis reaction are important driving forces for carbon deposition to occur locally when it is not expected based on the outlet CO concentration. Furthermore, correlation with a set of experimentally determined threshold operating points indicates that carbon deposition occurs primarily by the Boudouard reaction rather than by direct electrochemical reduction of CO or CO<sub>2</sub> to carbon for the studied cell type. Variation of fuel electrode porosity and thickness shows that these methods of reducing gas diffusion limitations widen the operating window that avoids carbon deposition.</p>},
  author       = {Navasa, Maria and Frandsen, Henrik Lund and Skafte, Theis Løye and Sundén, Bengt and Graves, Christopher},
  issn         = {0378-7753},
  keyword      = {Boudouard reaction,Carbon deposition,Multiphysics modeling,SOEC,Thermodynamic threshold},
  language     = {eng},
  month        = {08},
  pages        = {102--113},
  publisher    = {Elsevier},
  series       = {Journal of Power Sources},
  title        = {Localized carbon deposition in solid oxide electrolysis cells studied by multiphysics modeling},
  url          = {http://dx.doi.org/10.1016/j.jpowsour.2018.05.039},
  volume       = {394},
  year         = {2018},
}